During processing of sheet materials such as sheet metal, it is frequently necessary to subdivide rolls or pieces of sheet stock into narrower rolls or pieces. A slitter apparatus is typically employed for this purpose, with the apparatus including a plurality of cutting mechanisms which cut the sheet stock lengthwise to the desired narrower widths. An edge trimmer apparatus is typically employed on each side of the slitter to cut off the bad edges.
Attendant to slitting or edge trimming of sheet material in this fashion, it is common for opposite edge portions of the sheet stock to be cut, and recycled as scrap material. Because such pieces of scrap material have lengths corresponding to that of the original sheet stock, it is desirable to continuously cut the scrap edge portions as the slitter or trimmer apparatus is operated to slit the sheet stock.
Typical dual arbor scrap choppers utilize knives that are three-dimensional helical knives when mounted on the drum. Another type of knife blade used in dual arbor scrap choppers is a two-dimensional cutting knife blade that is made at least partially in the form of a radius and/or at least partially in the form of an ellipse. Such a knife blade and associated arbor is disclosed in co-owned U.S. Pat. No. 4,858,506, incorporated herein by reference.
Knife blades used in chopping scrap become dull with use and need to be sharpened. The knife blades are sharpened by removing material from at least one side of the knife blade adjacent the cutting edge. When the material is removed, a shim is required between the arbor and the knife blade to compensate for the loss of material and to ensure that the cutting edge remains in the proper location with respect to the arbor and to the opposite cutting edge of the knife blade mounted on the opposing arbor. The installation of the shims can be time consuming as the correct shim width must be determined and installed. These prior art systems will be discussed in greater detail below.
It would therefore be an advantage to provide a dual arbor chopper that utilized a knife in a manner that did not require shims throughout the life of the knife.